1. Field of the Invention
This invention relates to a pneumatic ratchet wrench, and more particularly to a pneumatic ratchet wrench having a shrunk head section.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a pneumatic ratchet wrench 1 disclosed in U.S. Pat. No. 6,640,669 includes a main body 11, a driving head 12 rotatable about a Z-axis and projecting from the main body 11, a ratchet unit 13, and two racks 14 each extending along a direction parallel to a central axis (X), and a motor assembly 15. The main body 11 has an intake passage 111 communicated fluidly with an air pressure source (not shown). The ratchet unit 13 includes a yoke 131 disposed around and geared to the driving head 12, a pawl 132 disposed between the driving head 12 and the yoke 131 and rotatable for controlling the rotational direction of the driving head 12, and a reverse gear 133 connected to the pawl 132. One of the racks 14 is operated by an external force to move between a meshing position, where it can rotate the reverse gear 133, and a non-meshing position, where it cannot rotate the reverse gear 133. The motor assembly 15 includes a cylinder 151 in fluid communication with the intake passage 111, a rotor 152 disposed pivotally within the cylinder 151 and driven pneumatically to rotate about an X-axis, and an eccentric shaft 153 connected between the rotor 152 and the yoke 131.
As such, when the eccentric shaft 153 is driven by the rotor 152 to rotate about the X-axis, the yoke 131 swings about the Z-axis to rotate the driving head 12 in a single direction for outputting a power.
Since the racks 14 are located respectively at two sides of the reverse gear 133, the width (L) of a front end portion of the main body 11 must be greater than maximum width of an assembly of the racks 14 and the reverse gear 133 such that the racks 14 and the ratchet unit 13 can be received within the front end portion of the main body 11. As a result, the front end portion of the main body 10 cannot be extended into a narrower space, thereby limiting the applicable range of the pneumatic ratchet wrench.